Build near Hitchin

[foxx]

Hi everybody,

I came on to this forum last year around May time to inquire about the build process of a pompeii oven, as myself and some friends had agreed to build one for a friend as a 40th Birthday present. After some wonderful advice, we set upon our build. Now, ordinarily most normal people would put up pics as the build takes place, where as i have decided to do the build and now upload some pics. Apologies.
As we have had to do this on a ridiculously tight budget, and absolutely no previous knowledge or experience in this, it was going to be interesting!
I would like to thank the many people on here whose builds have helped with ideas and suggestions.

We started with a 1m square base and a frame for the table top to go on, then we discovered that we had seriously under estimated the size, so built it out with another row of bricks. Anyway the pics will explain the build process. We ended up 1.2m table top, with a 30 inch internal diameter dome, with an opening of 15.5in by 9.5in.

You will see that once we got to the end of the build and went for a good fire, we made the schoolboy error of not having curing fires for the render layers and have now ended up with the small issue you will see at the end (please don't just rush to the end to see them, please look at the other pics)
One corner we did cut was not using an insulation blanket (budget reasons) as we thought the oven should still work, the fire may just require more wood and attention to keep the temp.

Anyway, I'll stop waffling and let you have a look. Please feel free to leave some thoughts, and possible ideas on how I can rectify the cracks. (I'm thinking some small holes drilled, more small fires, let it dry out, then another coat of render)

I hope I've uploaded the pics ok, apologies if not.

Thanks

Dave

[foxx]

Here are the next lot of pics

[foxx]

Next lot

[foxx]

Last lot of pics, including the damage. I look forward to your comments.

Regards

Dave

[awalker]

Very nice job indeed.

I promise i did not rush to the end

Sent from my GT-N5110 using proboards

[cannyfradock]

Hello Dave

First of all.....what a shame the render has cracked so much and even though you have cut a few corners the actual oven and the finish look superb.....well done!!

Now then...the problem finding...and a remedy.

The inner brickwork on many ovens...including my own...don't look so pretty after removing the forms, but a little bit of scraping away of old mortar and filling any voids with homebrew or lime mortar soon tidies up the top inner brickwork. This is easier said than done as it involves the chap in charge to use a tressel etc to be able to position him/herself to lay on his back inside the oven and fill the voids. (I try doing this with a trowel but usually end up donning a pair of marigold gloves and squidging in a pliable morter into all the surface area with my hand. I then, use a wet sponge to smooth off the whole area....a helper is definately needed for this part).

This brings us to the mortar used for laying the dome bricks (and the pointing after). I am assuming that you didn't use any powdered fire-clay in your mortar mix making the mortar a "homebrew" refractory mortar. If not It is always a good idea to use hydrated lime in the mortar?. I ask this as I would like you to check if the there is any large cracking from the internal brickwork. If there is then this can be addressed on the outer surface. ......I have heard of Pompeii ovens cracks opening up on the interior when fully firing but as the dome is a technical structure in itself, the dome can't actually go anywhere......or fail, so the cracks will always close up after firing.

If you do have this, then you need to cut away the vermecrete and render from that area and lay a strip of 4" wide ex-met over the crack with some lime mortar then re-do that area with vermecrete.

If you have no internal cracks....or nothing more than a few mm's then the cracking of the external render is due to either impatience in your curing fires or.....as a lack of the thermal blanket, the outer surface is getting too hot. In either case the solution FOR ME would be to leave the old render on but give it a good scratching or key, then lay some chicken wire over the whole dome (use your fingers or pliers to twist the chicken wire so it's sits as flat as possible on the dome...then give the dome another coat of lime render.....that should do the tricks.

I notice you have limited space near the edges of your slab, but the cracking problem isn't there so you should be able to squeeze in a full dome render coat .....just lay it thin near the perimeter.

I haven't got all the answer's....and I'm still learning but I hope my comments may be of some use to you.

Terry